The purpose of the proposed research is to study the physico-chemical aspects pertinent to the processes of demineralization and remineralizaton of dental enamel. Emphasis is given to the investigation of the role of salivary constituents and enamel composition in these processes. In particular, studies will be conducted on: 1. The effect of fluoride incorporation into hydroxyapatite on the nature and properties of pellicles formed by adsorption of salivary constituents (e.g. composition and permselectivity). 2. Adsorption of amino acids, peptides, proteins and salivary constituents onto fluoridated hydroxyapatites. Adsorption isotherms and mechanistic models to interpret adsorption results and gain insight into the selective adsorption process responsible for tooth pellicle formation. 3. Kinetics of calcium phosphate crystal growth attempting to develop a unified theory applicable to remineralization processes. Effects of additives, e.g. fluoride and salivary constituents, on the kinetics of crystal growth. 4. The factors involved in the demineralization of dental enamel, using demineralization buffers as well as pure cultures of cariogenic microorganisms. The effects of salivary pellicles developed on extracted teeth from fluoridated and non-fluoridated areas will be investigated. 5. The application of the information obtained in items 3) and 4) to the development of effective conditions for remineralization of dental enamel. Quantitative microradiography and polarized microscopy will be used in this connection.